St. Ann’s Sr. Sec. School Roorkee
Atoms and Molecules
CLASS 09 - SCIENCE
Section A 30) Define the atomic mass unit. [2]
31) Calculate the molar mass of (a) water (H2 O) (b) nitric acid
1) Define atomicity. [1] (HNO3 ). [2]
2) Which law of chemical combination deals with the composi- 32) What are polyatomic ions? Give examples . [2]
tion of compound? [1] 33) Which postulate of Dalton’s atomic theory is the result of
3) State the law of constant Proportion? [1] the law of conservation of mass? [2]
4) What is the atomicity of ammonia? [1] 34) Write down the formulae of:
5) What is an ion? Give one example. [1] i. Sodium oxide
6) How did Berzelius assign symbols to the elements? [1] ii. Aluminium chloride
7) An elements Z forms an oxide with formula Z2 O3 . What is iii. Sodium Sulphide
its valency? [1] iv. Magnesium hydroxide
8) What is the valency of calcium is CaCO3 ? [1] [2]
9) Calculate the formula unit mass of NaHCO3 . [1] 35) What are the failures of Dalton Atomic theory? [2]
10) Give an example of a triatomic molecule of an element. [1] 36) In a reaction, 5.3 g of sodium carbonate reacted with 6 g
11) Calculate the formula unit mass of CaCl2 . [1] of acetic acid. The products were 2.2 g of carbon dioxide,
12) What is Dalton? [1] 0.9 g water and 8.2 g of sodium acetic. Show that these
13) The valency of the of an element A is 4. Write the formula observations are in agreement with the law of conservation
of its oxide. [1] of mass.
14) Write the atomicity of the following molecules: sodium carbonate + acetic acid → sodium acetic + carbon
(a) H2 SO4 dioxides + water [2]
(b) CCI4 [1] 37) State the number of atoms present in each of the following
15) State law of conservation of Mass. [1] chemical species
16) An element X has valency 3 while the element Y has valency i. CO3 2 -
2. Write the formula of the compound between X and Y. ii. PO4 3 -
[1] iii. P2 O5
17) Define atomic mass unit [1] iv. CO
18) What are ions? What are its two types? [1] [2]
19) Express each of the following in kilograms: 38) Write the cations and anions present (if any) in the following
i. 5.84× 10 - 3 mg compounds:
ii. 58.34 g i. CH3 COONa
iii. 0.584 g ii. NaCl
iv. 5.873× 10 - 21 g iii. H2
[1] iv. NH4 NO3
20) Name the Indian philosopher who proposed the theory of [2]
matter. [1] 39) Why are chemical reactions according to law of conservation
21) Molecular mass of water is 18 u. What will be the number of mass? [2]
of molecules of water in 18 g water? [1] 40) i. Calculate the relative molecular mass of water (H2 O).
22) Formula of the carbonate of a metal M is M2 CO3 . Write ii. Calculate the molecular mass of HNO3 .
the formula of its chloride. [1] [2]
41) Calculate the mass percentage of oxygen present in the fol-
Section B lowing compounds and state the law of chemical combination
associated. Given, H=1, O=16.
23) What is meant by the term chemical formula? [2]
(i) Water (H2 O) and (ii) Hydrogen per oxide (H2 O2 ) [2]
24) How big are atoms? Explain it. [2]
42) The atomic mass of an element is in fraction. What does it
25) Which postulate of Dalton’s atomic theory can explain the
mean? [2]
law of definite proportions? [2]
43) Write the molecular formulae of all the compounds that can
26) What is the SI prefix for each of the following multiples and
be formed by the combination of following ions:
submultiples of a unit?
Cu2+ , Na+ , Fe3+ , Cl− , SO2−
4 , PO4
3−
[2]
i. 103
44) The mass of one molecule of a substance is4.65 × 10−23 g.
ii. 10 - 1
What is its molecular mass? What could this substance be?
iii. 10 - 2
[2]
iv. 10 - 6
45) What are ionic and molecular compounds? Give examples.
v. 10 - 9
[2]
vi. 10 - 12
46) State the Postulates of Dalton Theory. [2]
[2]
47) Why is not possible to see an atom with naked eye? [2]
27) Calculate the mass of one atom of hydrogen atom. [2]
48) Calculate the molecular Mass of
28) Which of the following elements A, B, C and D would you
i. Ammonium sulphate [(NH4 )2 SO4 ]
expect to be the most stable and why? Atomic number is
ii. Penicillin [C16 H18 N2 SO4 ]
given in brackets. A(8) , B(9), C (10), D(2). [2]
iii. Paracetamol [C8 H9 NO]
29) You are provided with a fine white coloured powder which
[2]
is either sugar or salt. How would you identify it without
49) What is the difference between the mass of a molecule and
tasting? [2]
Atoms and Molecules
CLASS 09 - SCIENCE
Section A 30) Define the atomic mass unit. [2]
31) Calculate the molar mass of (a) water (H2 O) (b) nitric acid
1) Define atomicity. [1] (HNO3 ). [2]
2) Which law of chemical combination deals with the composi- 32) What are polyatomic ions? Give examples . [2]
tion of compound? [1] 33) Which postulate of Dalton’s atomic theory is the result of
3) State the law of constant Proportion? [1] the law of conservation of mass? [2]
4) What is the atomicity of ammonia? [1] 34) Write down the formulae of:
5) What is an ion? Give one example. [1] i. Sodium oxide
6) How did Berzelius assign symbols to the elements? [1] ii. Aluminium chloride
7) An elements Z forms an oxide with formula Z2 O3 . What is iii. Sodium Sulphide
its valency? [1] iv. Magnesium hydroxide
8) What is the valency of calcium is CaCO3 ? [1] [2]
9) Calculate the formula unit mass of NaHCO3 . [1] 35) What are the failures of Dalton Atomic theory? [2]
10) Give an example of a triatomic molecule of an element. [1] 36) In a reaction, 5.3 g of sodium carbonate reacted with 6 g
11) Calculate the formula unit mass of CaCl2 . [1] of acetic acid. The products were 2.2 g of carbon dioxide,
12) What is Dalton? [1] 0.9 g water and 8.2 g of sodium acetic. Show that these
13) The valency of the of an element A is 4. Write the formula observations are in agreement with the law of conservation
of its oxide. [1] of mass.
14) Write the atomicity of the following molecules: sodium carbonate + acetic acid → sodium acetic + carbon
(a) H2 SO4 dioxides + water [2]
(b) CCI4 [1] 37) State the number of atoms present in each of the following
15) State law of conservation of Mass. [1] chemical species
16) An element X has valency 3 while the element Y has valency i. CO3 2 -
2. Write the formula of the compound between X and Y. ii. PO4 3 -
[1] iii. P2 O5
17) Define atomic mass unit [1] iv. CO
18) What are ions? What are its two types? [1] [2]
19) Express each of the following in kilograms: 38) Write the cations and anions present (if any) in the following
i. 5.84× 10 - 3 mg compounds:
ii. 58.34 g i. CH3 COONa
iii. 0.584 g ii. NaCl
iv. 5.873× 10 - 21 g iii. H2
[1] iv. NH4 NO3
20) Name the Indian philosopher who proposed the theory of [2]
matter. [1] 39) Why are chemical reactions according to law of conservation
21) Molecular mass of water is 18 u. What will be the number of mass? [2]
of molecules of water in 18 g water? [1] 40) i. Calculate the relative molecular mass of water (H2 O).
22) Formula of the carbonate of a metal M is M2 CO3 . Write ii. Calculate the molecular mass of HNO3 .
the formula of its chloride. [1] [2]
41) Calculate the mass percentage of oxygen present in the fol-
Section B lowing compounds and state the law of chemical combination
associated. Given, H=1, O=16.
23) What is meant by the term chemical formula? [2]
(i) Water (H2 O) and (ii) Hydrogen per oxide (H2 O2 ) [2]
24) How big are atoms? Explain it. [2]
42) The atomic mass of an element is in fraction. What does it
25) Which postulate of Dalton’s atomic theory can explain the
mean? [2]
law of definite proportions? [2]
43) Write the molecular formulae of all the compounds that can
26) What is the SI prefix for each of the following multiples and
be formed by the combination of following ions:
submultiples of a unit?
Cu2+ , Na+ , Fe3+ , Cl− , SO2−
4 , PO4
3−
[2]
i. 103
44) The mass of one molecule of a substance is4.65 × 10−23 g.
ii. 10 - 1
What is its molecular mass? What could this substance be?
iii. 10 - 2
[2]
iv. 10 - 6
45) What are ionic and molecular compounds? Give examples.
v. 10 - 9
[2]
vi. 10 - 12
46) State the Postulates of Dalton Theory. [2]
[2]
47) Why is not possible to see an atom with naked eye? [2]
27) Calculate the mass of one atom of hydrogen atom. [2]
48) Calculate the molecular Mass of
28) Which of the following elements A, B, C and D would you
i. Ammonium sulphate [(NH4 )2 SO4 ]
expect to be the most stable and why? Atomic number is
ii. Penicillin [C16 H18 N2 SO4 ]
given in brackets. A(8) , B(9), C (10), D(2). [2]
iii. Paracetamol [C8 H9 NO]
29) You are provided with a fine white coloured powder which
[2]
is either sugar or salt. How would you identify it without
49) What is the difference between the mass of a molecule and
tasting? [2]
